1. Field of the invention
The present invention relates to an improvement in a printing device, and more particularly to a printing device provided with cooling means suitable for a wire dot impact system.
2. Description of the prior art
In recent years, a wide variety of information processing instruments have been developed in accordance with demands for high efficiency in dealing with various kinds of business. With these progresses, printing devices of various systems have been developed.
The representative systems which have been employed in printing devices are, e.g., a wire dot impact system, an ink jet system, and a thermal recording system etc. The printing devices using the wire dot impact system, which is most popular among these systems, have an increasing requirement of low noise in addition to needs of improvement in printing quality and printing speed etc.
The wire dot impact system is operated by driving a plurality of wires by means of solenoids to effect printing operation, resulting in a loud operating noise.
Printing devices using the wire dot impact system are provided with cooling means in order to prevent seizure etc. of the printing head due to heat produced from the printing head.
A cooling fan driven by a motor is ordinarily employed as the cooling means. However, the fan's operating noise is felt to be extremely offensive to the ear in an office environment.
The prior art printing devices are configured such that the cooling fan becomes operative at the same time when the printing device is powered. Accordingly, the operating noise of the cooling fan occurs even when the printing head does not effect printing operation. In addition, because the operating noise is approximately proportional to air draft, there is a tendency that a printing device having a higher cooling effect exhibits a larger operating noise.
To eliminate noises due to the operation of the cooling fan when the printing head is inoperative, a method is proposed to tune the operation of the cooling fan to that of the printing head. However, there is a possibility that such a simple solution results in insufficient cooling effect.
For the reasons stated above, the conventional printing devices are required to always operate the cooling fan in order not to lower cooling effect. As a result, they are extremely noisy because of the operating noise of the cooling fan in addition to the operating noise of the printing head.